The definition of luck (or chance) varies by the philosophical, religious, mystical, and emotional context of the one interpreting it; according to the classic Noah Webster's dictionary, luck is "a purposeless, unpredictable and uncontrollable force that shapes events favourably or unfavourably for an individual, group or cause".[1] Yet the author Max Gunther defines it as "events that influence one's life and are seemingly beyond one's control".[2]

When thought of as a factor beyond one's control, without regard to one's will, intention, or desired result, there are at least two senses that people usually mean when they use the term, the prescriptive sense and the descriptive sense. In the prescriptive sense, luck is a supernatural and deterministic concept that there are forces (e.g. gods or spirits) that prescribe that certain events occur very much the way laws of physics will prescribe that certain events occur. It is the prescriptive sense that people mean when they say they "do not believe in luck". In the descriptive sense, people speak of luck after events that they find to be fortunate or unfortunate, and maybe improbable.

The English noun luck appears comparatively late, during the 1480s, as a loan from Low German (Dutch or Frisian) luk, a short form of gelucke (Middle High Germangelücke). Compare to old Slavic word lukyj (лукый) - appointed by destiny and old Russian luchaj (лучаи) - destiny, fortune. It likely entered English as a gambling term, and the context of gambling remains detectable in the word's connotations; luck is a way of understanding a personal chance event. Luck has three aspects[5][6] which make it distinct from chance or probability.[7]

Before the adoption of luck at the end of the Middle Ages, Old English and Middle English expressed the notion of "good fortune" with the word speed (Middle English spede, Old English spēd); speed besides "good fortune" had the wider meaning of "prosperity, profit, abundance"; it is not associated with the notion of probability or chance but rather with that of fate or divine help; a bestower of success can also be called speed, as in "Christ be our speed" (William Robertson, Phraseologia generalis, 1693).

The notion of probability was expressed by the Latin loanword chance, adopted in Middle English from the late 13th century, literally describing an outcome as a "falling" (as it were of dice), via Old French cheance from Late Latin cadentia "falling". Fortuna, the Roman goddess of fate or luck, was popular as an allegory in medieval times, and even though it was not strictly reconcilable with Christian theology, it became popular in learned circles of the High Middle Ages to portray her as a servant of God in distributing success or failure in a characteristically "fickle" or unpredictable way, thus introducing the notion of chance.

Luck refers to that which happens to a person beyond that person's control. This view incorporates phenomena that are chance happenings, a person's place of birth for example, but where there is no uncertainty involved, or where the uncertainty is irrelevant. Within this framework, one can differentiate between three different types of luck:

Constitutional luck, that is, luck with factors that cannot be changed. Place of birth and genetic constitution are typical examples.

Another view holds that "luck is probability taken personally." A rationalist approach to luck includes the application of the rules of probability and an avoidance of unscientific beliefs. The rationalist thinks that the belief in luck is a result of poor reasoning or wishful thinking. To a rationalist, a believer in luck who asserts that something has influenced his or her luck commits the "post hoc ergo propter hoc" logical fallacy: that because two events are connected sequentially, they are connected causally as well. In general:

A happens (luck-attracting event or action) and then B happens;
Therefore, A influenced B.

More contemporary authors writing on the subject believe that the definition of good destiny is: One who enjoys good health; has the physical and mental capabilities of achieving his goals in life; has good appearance, and; has happiness in mind and is not prone to accidents.[10]

In the rationalist perspective, probability is only affected by confirmed causal connections.

The gambler's fallacy and inverse gambler's fallacy both explain some reasoning problems in common beliefs in luck. They involve denying the unpredictability of random events: "I haven't rolled a seven all week, so I'll definitely roll one tonight".

There is also a series of spiritual, or supernatural beliefs regarding fortune. These beliefs vary widely from one to another, but most agree that luck can be influenced through spiritual means by performing certain rituals or by avoiding certain circumstances.

Luck can also be a belief in an organization of fortunate and unfortunate events. Luck is a form of superstition which is interpreted differently by different individuals. Carl Jung coined the term synchronicity, which he described as "a meaningful coincidence".

What will happen to you for offering food and wine to the gods you call good luck and fate? Your luck will end.

Belief in the extent of Divine Providence varies; most acknowledge providence as at least a partial, if not complete influence on luck. Christianity, in its early development, accommodated many traditional practices which at different times, accepted omens and practiced forms of ritual sacrifice in order to divine the will of their supreme being or to influence divine favoritism. The concepts of "Divine Grace" or "Blessing" as they are described by believers closely resemble what is referred to as "luck" by others.

Mesoamerican religions, such as the Aztecs, Mayans and Incas, had particularly strong beliefs regarding the relationship between rituals and the gods, which could in a similar sense to Abrahamic religions be called luck or providence. In these cultures, human sacrifice (both of willing volunteers and captured enemies), as well as self-sacrifice by means of bloodletting, could possibly be seen as a way to propitiate the gods and earn favor for the city offering the sacrifice. An alternative interpretation[11] would be that the sacrificial blood was considered as a necessary element for the gods to maintain the proper working order of the universe, in the same way that oil would be applied to an automobile to keep it working as designed.

Many traditional African practices, such as voodoo and hoodoo, have a strong belief in superstition. Some of these religions include a belief that third parties can influence an individual's luck. Shamans and witches are both respected and feared, based on their ability to cause good or bad fortune for those in villages near them.

Some encourage the belief in luck as a false idea, but which may produce positive thinking, and alter one's responses for the better. Others, like Jean-Paul Sartre and Sigmund Freud, feel a belief in luck has more to do with a locus of control for events in one's life, and the subsequent escape from personal responsibility. According to this theory, one who ascribes their travails to "bad luck" will be found upon close examination to be living riskylifestyles. In personality psychology, people reliably differ from each other depending on four key aspects: beliefs in luck, rejection of luck, being lucky, and being unlucky.[12] People who believe in good luck are more optimistic, more satisfied with their lives, and have better moods.[12] If "good" and "bad" events occur at random to everyone, believers in good luck will experience a net gain in their fortunes, and vice versa for believers in bad luck. This is clearly likely to be self-reinforcing. Thus, a belief in good luck may actually be an adaptive meme.

A game may depend on luck rather than skill or effort. For example, chess does not involve any random factors such as throwing dice, while dominoes has the "luck of the draw" when selecting tiles. In poker, especially games with a communal board, pure luck may decide a winning hand. Luck in games involving chance is defined as the change in a player's equity after a random event such as a die roll or card draw.[13] Luck is positive (good luck) if the player's position is improved and negative (bad luck) if it is worsened. A poker player who is doing well (playing successfully, winning) is said to be "running good".[14] There is, currently, no academic research as to explain how some profitable players who ascribe their profitability to a mix of probability and chance understand luck in the game.

In baseball, it is unusual for the best team in the league to win the World Series.[citation needed] Experts from statisticians to oddsmakers say chance plays an unusually big part in the game, partly because play is spread out over such a large area.[citation needed] The game's complexity is also relevant: The scoring value of a base hit, for instance, depends largely on factors outside the hitter's control—namely the ability of the previous batters to get on base.

Many countries have a national lottery. Individual views of the chance of winning, and what it might mean to win, are largely expressed by statements about luck. For example, the winner was "just lucky" meaning they contributed no skill or effort.

Most cultures consider some numbers to be lucky or unlucky. This is found to be particularly strong in Asian cultures, where the obtaining of "lucky" telephone numbers, automobile license plate numbers, and household addresses are actively sought, sometimes at great monetary expense. Numerology, as it relates to luck, is closer to an art than to a science, yet numerologists, astrologists or psychics may disagree. It is interrelated to astrology, and to some degree to parapsychology and spirituality and is based on converting virtually anything material into a pure number, using that number in an attempt to detect something meaningful about reality, and trying to predict or calculate the future based on lucky numbers. Numerology is folkloric by nature and started when humans first learned to count. Through human history it was, and still is, practiced by many cultures of the world from traditional fortune-telling to on-line psychic reading.

Different thinkers like Thomas Kuhn have discussed the role of chance in scientific discoveries. Richard Wiseman did a ten-year scientific study into the nature of luck that has revealed that, to a large extent, people make their own good and bad fortune. His research revealed that "Lucky people generate their own good fortune via four basic principles. They are skilled at creating and noticing chance opportunities, making lucky decisions by listening to their intuition, creating self-fulfilling prophecies via positive expectations, and adopting a resilient attitude that transforms bad luck into good."[15] Researchers have suggested that good luck and good mood often co-occur (Duong & Ohtsuka, 2000)[16] and that lucky people are happy and optimistic whereas unlucky people feel anxious and depressed (Day & Maltby, 2003; Wiseman, 2003).[15][17]

Although previous studies have explored the antecedences and consequences of luck using attribution theory (e. g., Fischoff, 1976; Weiner et al., 1987),[18][19] personality variables (Darke & Freedman, 1997a;b),[20] and more recently a cognitive priming approach (DeMarree et al., 2005; Kramer & Block, 2008) research on the underlying mechanism of how luck influences consumer judgment and behavior has been noticeably absent in the extant literature. Moreover, in much of this previous work, luck is manipulated in a way that is very likely to elicit positive affect as well. Thus, it is difficult to articulate whether the observed effects of luck are due to chronic beliefs about luck, temporary changes in how lucky people feel, or because of changes caused by the positive affect that is experienced. Their research showed that priming participants subliminally with luck-related stimuli made them feel luckier and happier. It was also found that the effects of priming luck using subliminal messages increased participants' estimates of the likelihood of favorable events, their participation in lotteries, the amount of money they invested in relatively risky financial options and these effects appeared to be mediated by temporary changes in perceptions of luck rather than by affect).[21][22]

Gautama Buddha, the founder of Buddhism, taught his followers not to believe in luck. He taught that all things which happen must have a cause, either material or spiritual, and do not occur due to luck, chance or fate. The idea of moral causality, karma (Pali: kamma), is central in Buddhism. In the Sutta Nipata, the Buddha is recorded as having said the following about selling luck:

Whereas some religious men, while living of food provided by the faithful make their living by such low arts, such wrong means of livelihood as palmistry, divining by signs, interpreting dreams ... bringing good or bad luck ... invoking the goodness of luck ... picking the lucky site for a building, the monk Gautama refrains from such low arts, such wrong means of livelihood. D.I, 9–12[23]

However, belief in luck is prevalent in many predominantly Buddhist countries. In Thailand, Buddhists may wear verses (takrut) or lucky amulets which have been blessed by monks for protection against harm.[24]

In Hinduism it is said that by proper worship, with a meticulous prayer procedure (Sanskrit: Shri Lakshmi Sahasranam Pujan Vidhi) the blessings of Lakshmi, the Hindu goddess of money and fortune, may be obtained. Lakshmi Parayan (prayer) is performed in most Hindu homes on the day of Diwali, the festival of lights. At that time also Rangoli are drawn, decorative designs on floors of living rooms and courtyards during Hindu festivals that are meant as a sacred welcoming area for the luck.

There is no concept of luck in Islam other than actions determined by Allah based on the merit of the choice made by human beings. It is stated in the Qur'an (Sura: Adh-Dhariyat (The Wind that Scatter) verse:22) that one's sustenance is pre-determined in heaven when the Lord says: "And in the heaven is your provision and that which ye are promised." However, one should supplicate towards Allah to better one's life rather than hold faith in un-Islamic acts such as using "lucky charms". However, in Arabic language there is a word which directly means "luck", which is حظḥaẓẓ, and a related word for "lucky", محظوظmaḥẓūẓ. It is also forbidden to believe in luck or anything else related to luck, as it is classified as shirk (associating partners of Allah or giving any share of any attribution which belongs to Allah and Allah alone).

The Tunisians retain some native beliefs of Berber origin such as the evil eye.[25] A number of practices, such as shutters painted blue are also used to repel evil spirits.[26]

Donald Duck's cousin Gladstone Gander, created by Carl Barks in 1948, is known for his extreme good fortune that causes him to be given anything he wants without any effort. There have been different versions how he got so lucky, Carl Barks tells in his story Luck of the North that Gladstone was born under a lucky star, while Don Rosa tells that he inherited his luck from his mother, who got it from a distelfink symbol when she was born. In many Italian comics Gladstone is extremely lucky because the goddess Fortuna is in love with him.

In Larry Niven's novel Ringworld, the character Teela Brown was the incredibly lucky result of a centuries-long breeding program initiated by the alien Pierson's Puppeteers directed to just such an outcome. The consequence of her state was that she had led such a charmed and worry-free life that she was emotionally immature and unprepared for "harsh reality."

The premise of the 2001 Spanish thriller film Intacto is that luck can be amassed and transferred as any other commodity and fortune flows from those who have less to those who have more.

While the video game Fallout: New Vegas depicts Luck as a statistic (one of seven that define characters), one character offers an implant called a Probability Calculator. Its effect is similar to that described in Science above, allowing its recipient to understand probabilities better. Notably, one of the major non-player characters, Robert House, has a perfect luck score, and in-story had done everything from calculating the date of a nuclear war (being off by mere hours) and taking control of a 'vault' fallout shelter in a game of chance.

In the Danganronpa franchise, Makoto Naegi, Nagito Komaeda, and Izuru Kamukura all possess a talent which grants them uncommonly good fortune and therefore were given the title of "Ultimate Lucky Student."

^Elbow Room by Daniel Clement Dennett, p. 92. "We know it would be superstitious to believe that "there actually is such a thing as luck" - something a rabbits' foot might bring - but we nevertheless think there is an unsuperstitious and unmisleading way of characterizing events and properties as merely lucky."

^Luck: the brilliant randomness of everyday life p. 32. "Luck accordingly involves three things: (1) a beneficiary or maleficiary, (2) a development that is benign (positive) or malign (negative) from the stand point of the interests of the affected individual, and that, moreover, (3) is fortuitous (unexpected, chancy, unforeseeable.)"

^CHANCE News 4.15 ...the definition in the Oxford English dictionary: "the fortuitous happening of an event favorable or unfavorable to the interest of a person"

^Miller, Ed (Nov 27, 2009). "The Pitfalls of Running Good". CardPlayer.com. Retrieved 11 April 2014. I’ve always thought that one of the worst things that can happen to new poker players is for them to run really good right out of the gate. If they rack up a number of big wins early on, a couple of bad things can happen.